Hydrogen fuel refers to use of hydrogen for its combustive qualities as a fuel and energy carrier. The hydrogen must first be broken out from its compound form with oxygen as water (H2O) using electrolysis or gathered by other means as it does not naturally occur by itself. Hydrogen cannot be mined or drilled as with fossil fuels and requires more energy input to produce it than is generated with its combustion.

Advocates of hydrogen fuel believe solar power, wind power or other renewable and environmentally friendly technologies can be used to make hydrogen fuel. The hydrogen can then be transported and used for various applications. This might have environmental advantages over burning fossil fuels for motive power and other uses.

Hydrogen is a potential fuel for motive power, including cars, boats and airplanes. It can also be used in smaller devices using fuel cells. Some environmentalists believe a hydrogen economy could greatly reduce the emission of carbon dioxide and therefore play a major role in tackling global warming. Countries without oil, but with renewable energy resources could use hydrogen as a clean burning energy store.